Abstract
The effects of 0.7 wt.% Si addition on the microstructural evolution, hardness, creep resistance, and shear strength of AZ61 alloy were investigated in the temperature range 298-523 K. Creep behavior was assessed by impression creep test, and ultimate shear strength (USS) was measured by the shear punch test (SPT). The as-cast structure of AZ61 consists of α-Mg matrix and the β-Mg₁₇Al₁₂ intermetallic phase. Due to the low thermal stability of this phase, the hardness and strength of AZ61 significantly decreased as the temperature increased. The results showed that hot hardness, creep resistance and high-temperature shear strength of the base alloy were significantly enhanced with the addition of Si. This was attributed to the reduction in the volume fraction of β-Mg₁₇Al₁₂ and formation of the more thermally stable Mg₂Si intermetallic particles. These particles have a Chinese script morphology which reduce ductility but act as the main strengthening agent in the investigated system, by strengthening the matrix of the base alloy and hindering grain growth during deformation.

Key words
AZ61 Mg alloy, shear strength, creep, hardness

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